Metastasis is a major cause of mortality in cancer patients. The ability of cancer cells to invade the surrounding extracellular matrix is an important aspect of this complex, multistep process. The central theme of this proposal is to examine the effect of a two-pronged attack on tumor invasion and metastasis by inhibiting the first two steps of the postulated three steps involved in tumor invasion: (1) attachment of tumor cells to the extracellular matrix via specific cell surface receptors (integrins), (2) proteolytic degradation of the extracellular matrix and (3) locomotion through the proteolytically modified matrix. Inhibition of attachment will be explored using small disulfide-rich peptides from snake venoms, called disintegrins, that act to block the binding of extracellular matrix proteins to their integrin receptors on the surface of tumor cells. Inhibition of proteolytic degradation of the extracellular matrix will be accomplished using a recombinant inhibitor of metalloproteinases called metalloproteinase inhibitor/tissue inhibitor of metalloproteinases-2 (MI/TIMP-2). Studies will focus on the purification of disintegrins and on the characterization of their binding to the cell surface of invasive and metastatic cell lines. We will then examine the effect of the disintegrins used either alone or in combination with rTIMP-2 on tumor invasion in vitro and tumor metastasis in vivo. These studies will determine the effect of an interesting and important combination of two inhibitors of tumor invasion and metastasis that act at different steps in the multistep process involved in tumor dissemination. They will represent the combined effort of an investigator (PI) with expertise in cell biology of metastasis and metalloproteinase inhibitors and a protein chemist (co-PI) who has studied snake venom proteins for a number of years.